At least not on XP SP2 or SP3 on XP Home. If you try

HANDLE hEvent = OpenEvent(SYNCHRONIZE, FALSE, _T("Global\\TermSrvReadyEvent"));

hEvent is set to NULL, and GetLastError returns 5 (access denied).

You can do this on Vista Business on a limited user account though.

Private Declare Function WTSRegisterSessionNotification Lib "Wtsapi32" (ByVal hWnd As IntPtr, ByVal THISSESS As Integer) As Integer
Private Const NOTIFY_FOR_ALL_SESSIONS As Integer = 1
Private Const NOTIFY_FOR_THIS_SESSION As Integer = 0

Usage:

  
After regustering owerride your WndProc anc catch WM_WTSSESSION_CHANGE message like this:
  
Private Const WM_WTSSESSION_CHANGE As Integer = &H2B1

    Private Enum WTS
        CONSOLE_CONNECT = 1
        CONSOLE_DISCONNECT = 2
        REMOTE_CONNECT = 3
        REMOTE_DISCONNECT = 4
        SESSION_LOGON = 5
        SESSION_LOGOFF = 6
        SESSION_LOCK = 7
        SESSION_UNLOCK = 8
        SESSION_REMOTE_CONTROL = 9
    End Enum
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        Select Case m.Msg
            Case WM_WTSSESSION_CHANGE
                Select Case m.WParam.ToInt32
                    Case WTS.CONSOLE_CONNECT
                        Debug.Print("A session was connected to the console session.")
                    Case WTS.CONSOLE_DISCONNECT
                        Debug.Print("A session was disconnected from the console session.")
                    Case WTS.REMOTE_CONNECT
                        Debug.Print("A session was connected to the remote session.")
                    Case WTS.REMOTE_DISCONNECT
                        Debug.Print("A session was disconnected from the remote session.")
                    Case WTS.SESSION_LOGON
                        Debug.Print("A user has logged on to the session.")
                    Case WTS.SESSION_LOGOFF
                        Debug.Print("A user has logged off the session.")
                    Case WTS.SESSION_LOCK
                        Debug.Print("A session has been locked.")
                    Case WTS.SESSION_UNLOCK
                        Debug.Print("A session has been unlocked.")
                    Case WTS.SESSION_REMOTE_CONTROL
                        Debug.Print("A session has changed its remote controlled status. To determine the status, call GetSystemMetrics and check the SM_REMOTECONTROL metric.")
                End Select
        End Select
        MyBase.WndProc(m)
    End Sub 

It seems that NOTIFY_FOR_THIS_SESSION flag of this function doesnot do what it is meant to under certain conditions. This problem was seen in Windows XP SP2 but has not been tested in any other Windows OS versions.

Scenario 1 (Where it works as it is supposed to):
Try calling WTSRegisterSessionNotification() with NOTIFY_FOR_THIS_SESSION flag set in your program. Then goto 'Start->Log Off' then click on 'Switch User'. Now select a new user. Then keeping this new account open (which will be required to be so for scenario 2) switch back to your original user account. You will have received WTS_SESSION_LOCK and WTS_SESSION_UNLOCK as expected; both events related to the session from where your code is running.

Scenario 2 (Where it fails to work as it is supposed to):
Now restart your program and again goto 'Start->Log Off' then 'Switch User'. This time unlock the new account you had locked earlier. Again switch to your original account to see what messages your window has got. This time too WTS_SESSION_LOCK and WTS_SESSION_UNLOCK will have been caught. But there is a problem. WTS_SESSION_LOCK is fired correctly for the original session but WTS_SESSION_UNLOCK will have been fired while unlocking the new account and no event will have fired when the user is unlocking the session where your program is running (whom you asked to be notified for its lock/unlock event).

This problem is easily confirmed if you call WTSGetActiveConsoleSessionId() when lock and unlock events are caught in your code. You will see that you get different session ids in Scenario 2 instead of being same.


Solution:
To be notified correctly of session change events concerning only your session, save session id of your process by calling GetCurrentProcessId() and ProcessIdToSessionId() function in a variable. Also, call WTSRegisterSessionNotification() with NOTIFY_FOR_ALL_SESSIONS (Even a process running under guest account can receive notifications of global session change under Windows XP SP2; not tested in any otherOS vers). When you receive WM_WTSSESSION_CHANGE message in your windows procedure, see if WTSGetActiveConsoleSessionId() and session id of your process (which you saved earlier in a variable) are equal or not. If they are equal then this event is concerned with your session.

Happy Coding,
Sanje2v